This invention relates to a coupling for connecting pipes provided with exterior connection grooves. More particularly, this invention relates to an improvement by which a standard or conventional coupling, which is normally utilized to couple pipes of equal diameter, may be used to couple one pipe, which is of the diameter for which the coupling is intended, to a smaller diameter pipe, by utilizing a changeable insert whose size is matched to the smaller diameter pipe.
It is conventional to connect adjacent ends of axially aligned pipes by means of a circular shaped coupling which encircles the adjacent pipe ends. Usually, that type of coupling is formed of two semi-circular segments which are bolted together to form the complete circle. The couplings segments are of a U-shaped cross-section to provide an annular, inwardly opening channel. Each of the ends of the legs that define the groove forms a key or tenon which fits into a groove formed in the surfaces of each of the pipes. A suitable gasket, arranged within the annular channel defined by the coupling segments, serves to seal the joint formed by the coupling and the adjacent pipe ends.
This type of coupling is normally used where pipes are to be connected together with some degree of flexibility in the joint. This flexibility or the ability of the pipe ends to move slightly, relative to each other, results from the relatively loosely interfitting coupling leg tenons and the pipe grooves and the resilient gasket which seals the pipe ends within the coupling.
In the type of coupling described, the coupling channel forming legs are usually of the same length, measured radially inwardly, so as to couple pipes of equal diameter. Thus, plumbing contractors and suppliers, must stock a substantial number of different diameter couplings so that they are readily available for coupling various diameter pipes which may be used in a particular plumbing installation.
In cases where it is necessary to couple a larger diameter pipe to a smaller diameter pipe, the same type of coupling is used. However, here, the coupling U-shaped channel is formed with legs of unequal length. That is, one leg is shorter than the other, measured in the radially inward direction. This permits the shorter leg to closely encircle the larger diameter pipe and the longer leg to closely encircle the smaller diameter pipe. An example of this type of coupling is disclosed in U.S. Pat. No. 3,680,894 issued Aug. 1, 1972 to Young for "Joints Between Pipes of Different Diameters and Couplings and Gaskets for Same."
Because of the wide variation in diameters of larger and smaller couple pipes which may be found in different plumbing installations, it is necessary for plumping contractors and their supplies to stock a very large inventory of couplings having different length legs to couple different diameter pipes. By way of example, it may be desirable to couple a 6 inch O.D. pipe to a 4 inch O.D. at one point; a 6 inch O.D. pipe to a 31/2 diameter pipe elsewhere; and a 6 inch O.D. pipe to a 21/2 inch O.D. in another place, etc. Thus, it can be seen that a single diameter large pipe may be coupled to a wide variety of diameters of smaller pipes. This necessitates having available a series of couplings for that purpose. Likewise, since the larger diameter pipes may also vary, the number of large to small diameter couplings are multiplied. That is in addition to the need for an inventory of couplings for connecting pipes of the same O.D., e.g. for connecting a 6 inch O.D. pipe to another 6 inch O.D. pipe.
Couplings of this type are generally formed by casting molten metal either in sand molds, using patterns, or in permanent molds. In either event, it is necessary for the manufacturer to inventory a large number of patterns or permanent molds to handle the wide variety of size couplings needed for connecting the wide variety of different diameter large and small pipes that may be connected together in installations. Thus, this invention concerns an improvement by which standard couplings that are intended for connecting equal diameter pipes may be inexpensively and easily converted for coupling different size pipes so that it is unnecessary to inventory couplings for connecting pipes of different diameters.